Make "update-cache --refresh" do what it really should do: just refresh the "stat" information.
Make "update-cache --refresh" do what it really should do: just
refresh the "stat" information.

We need this after having done a "read-tree", for example, when the
stat information does not match the checked-out tree, and we want to
start getting efficient cache matching against the parts of the tree
that are already up-to-date.

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git